I agree with n4sxx. Unless the sign is state compliant, go in and go about your business. No one is going to know(that's the whole idea). You are not going to be frisked, and even if it was found out, they will ask you to leave, and IF on the outside chance the LEO's are involved, you can express that the sign is not state compliant, and when you were asked to leave, you did so. I carry a copy of what the sign should look like, and none of the places I have been to that post an anti-conceal carry sign are within state regulations. And if the sign was, then you go to the next establishment. Contact the their main branch or mother company, and find out what their company policy is. If it doesn't jive with our 2A, then put it on a list and extend the info to the rest of us, because I will not put money into the pockets of such places. When I go visit my parents in N.J., I make sure that I have enough fuel to get through MD., because I will not stop to get gas, buy a drink or food of any kind, etc. The only reason I spend money in N.J. is my folks living there, and I try to limit what I spend there.
There was a story not to long ago about a manager of a Wal-Mart that erroneously posted a "no carry sign", and the person who was carrying called Wal-Marts main office, and that manager was made to take the sign down. Sometimes we have managers that take liberties that are not company policy.
"Nemo me impune lacessit"